1. Field of the Invention
The present invention is directed to certain 2-substituted adenosine derivatives which have beneficial cardiovascular and antihypertensive activity in mammals, including humans and domestic animals. The present invention is also directed to a process for making said compounds.
2. Brief Description of the Prior Art
Adenosine has been known for a long time to possess certain cardiovascular, and particularly coronary dilator activity. In an effort to obtain adenosine analogs of greater potency, or longer duration of activity, or both, many analogs of this naturally occurring nucleoside have been synthesized and tested.
Moreover, numerous studies have been conducted in order to elucidate the biochemical mechanism of action of adenosine and its analogs, and several theories and hypotheses have been proposed regarding biochemical pathways and receptor sites.
For discussion of current theories regarding the foregoing, reference is made to the following articles and publications: Adenosine Receptors: Targets for Future Drugs, by John W. Daly, Journal of Medicinal Chemistry, 25, 197 (1982); Cardiovascular Effects of Nucleoside Analogs, by Herman H. Stein and Pitambar Somani, Annals New York Academy of Sciences, 225, 380 (1979); Coronary Dilatory Action of Adenosine Analogs: a Comparative Study, by G. Raberger, W. Schutz and O. Kraupp. Archives internationales de Pharmacodynamie et de Therpie 230, 140-149 (1977); chapter 6 of the book titled: Regulatory Function of Adenosine, (pages 77-96), R. M. Berne, T. W. Rall and R. Rubio editors, Martinus Nijhoff publishers, The Hague/Boston/London; and Ethyl Adenosine-5'-carboxylate. A Potent Vasoactive Agent in the Dog, by Herman H. Stein, Journal of Medicinal Chemistry, 16, 1306 (1973); Modification of the 5' Position of Purine Nucleosides. 2. Synthesis and Some Cardiovascular Properties of Adenosine-5'(N-substituted)carboxamides, by Raj. N. Prasad et al., Journal of Medicinal Chemistry, 23 313 (1980), and Modification of the 5' Position of Purine Nucleosides. 1. Synthesis and Biological Properties of Alkyl Adenosine-5'-carboxylates by Raj N. Prasad et al., Journal of Medicinal Chemistry, 19, 1180 (1976).
Still more adenosine derivatives having beneficial cardiovascular activity are described in another application for United States Letters Patent of the present inventors, Ser. No. 601,435, filed on Apr. 18, 1984, now abandoned, Ser. No. 742,565, filed on Jun. 12, 1985, and Ser. No. 625,450, filed on Jun. 28, 1984.
Adenosine receptors have been subdivided into two subtypss: A.sub.1 receptors, which inhibit adenylate cyclase, and A.sub.2 receptors, which stimulate adenylate cyclase. It is thought that coronary vasodilation is mediated by A.sub.2 receptor activation [see, e.g., Haleen, S., et. al., Life Sci., 36, 127-137 (1985)]. In order to minimize side effects associated with activation of A.sub.1 receptors, it is a goal of pharmaceutical research to identify compounds highly selective for A.sub.2 receptors.
Among a series of related compounds, one early compound claimed to possess coronary vasodilatory activity was 2-phenylaminoadenosine (CV-1808) [see Marumoto, R., et. al., Chem. Pharm. Bull., 23, 759 (1975)]. More recently, a series of N.sup.6 -substituted adenosine derivatives were disclosed as having high A.sub.2 affinity and selectivity [see Trivedi, B. K., et. al., J. Med. Chem., 31, 271-273 (1988), and Bridges, A., et. al., J. Med. Chem., 31, 1282-1285 (1988)]. Another series of 2,5'-disubstituted adenosine derivatives have been disclosed as A.sub.2 agonists (European Patent Application EP-277-917-A).
Many of the known adenosine derivatives are less than satisfactory as theraupeutics agents, due to low activity, short duration of effect, toxicity or undesirable side effects. In this light, there is a continuing interest in identifying agents which possess an desired profile of highly selective and potent adenosine A.sub.2 receptor activity with minimal toxicity. The compounds of the present invention constitute a step in this direction.